-Dan dos Santos
Now that we know how to avoid the dangers of Solvents, let's discuss WHY we need to. First, some facts, as well as common misconceptions, about the hazards of turpentine.

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-Turpentine is made from tree sap.

True.

Turpentine is made from the distilled resin of Pine trees. It is actually all-natural, wether or not it says so on the label.

-Turpentine is cancerous.

False.

Turpentine is TOXIC, and -can- kill you. Even short term exposure can have really bad effects, such as asphyxiation. However, long term exposure has not been proven to cause CANCER.

-Turpentine has health benefits.

True.

Turpentine has long been used as a home remedy for respiratory problems. Still today, Vicks Vaporub contains turpentine.

-Low-odor turpentine is safer that regular turpentine.

False.

Just because you can't smell it, doesn't make it less dangerous. In fact, toxic exposure is -more- likely with low-odor turpentine, because you may be unaware of it's presence. However, Odorless Mineral Spirits (which is a turpentine substitute derived from petroleum), is much less dangerous.

-I need to use turpentine if I want to thin my paint.

False.

Oils paint can be thinned with additional oil.

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Well... That's the good. So now you may be asking yourself, "If turpentine is all-natural, what's the big deal?" The problem is, even all-natural things can kill you... like bears, and mushrooms, and turpentine.

According to OSHA, The effects of turpentine on humans are as follows:

Turpentine is a skin, eye, mucous membrane, and upper respiratory tract irritant in humans. It may also cause skin sensitization and central nervous system, gastrointestinal, and urinary tract effects.

The lowest estimated oral dose reported to be lethal in humans is 441 mg/kg. Exposure to a 75-ppm concentration for 3 to 5 minutes irritates the nose and throat, and exposure to a 175-ppm concentration irritates the eyes and may be considered intolerable by human volunteers.

Ingestion of turpentine causes a burning pain in the mouth and throat, nausea, vomiting, diarrhea, abdominal pain, excitement, ataxia, confusion, stupor, seizures, fever, and tachycardia and may cause death due to respiratory failure.

Toxic glomerulonephritis and bladder irritation, with hematuria, albuminuria, oliguria, and dysuria, have been associated with overexposure to the vapor of turpentine in the past; however, the more purified form of turpentine now in use appears to have decreased the incidence of or to have eliminated turpentine-induced nephritis.

Splashes of the liquid in the eye produce severe pain and blepharospasm; conjunctival redness and temporary corneal erosion may also occur, but these effects are reversible. Chronic skin exposure to turpentine may produce a hypersensitivity reaction, with bullous dermatitis and/or eczema.

A case-control study of workers in particle-board, plywood, sawmill, and formaldehyde glue factories demonstrated a statistically significant association between chronic exposure (longer than 5 years) to terpenes (the principal component of turpentine) and the development of respiratory tract cancers.

So even though turpentine is pretty darn bad for you, the good news is that you can usually tell that it's doing something bad. If you can identify the problem, it's a lot easier to rectify it.

Now, some people have incredible tolerances for harmful things (me, not so much). It's quite possible that you could work in a studio FILLED with turpentine fumes for a lifetime and never have a problem. It's also quite possible that your Grandmother smoked 20 cigarettes a day for 90 years and lived to be 105. However, many (if not most) people will develop breathing problems, skin rashes and migraines when exposed to turpentine in levels that are quickly achieved when painting with oils in an enclosed room.

So what do you do about it? Well, like Justin said in part 1, you try to minimize the amount of vapor in the air. You can do this two ways:
1. Increase the amount of air.
2. Decrease the amount of vapors.

Personally, my primary approach consists of #2.

I never, ever, ever, paint with an open jar of turpentine in my studio. Not even to clean my brushes. I do however, use a small jar of medium, consisting of equal parts odorless mineral spirits and linseed oil.

(Odorless mineral spirits [also known as OMS] is an alternative solvent, which evaporates slower than turpentine, and is FAR less toxic. However, it is also not as potent a solvent, and therefore cannot be used to dissolve certain resins, like Damar.)

Why the mixture? Oils can be diluted with the addition of other oils, but they can not be dissolved. This is important when dealing with fat and lean layers of paint. Basically, a lean layer has more solvent. A fat layer has more oil. By mixing the two together, I achieve neutrality... a good thing for a painting medium to be.

But the mixture serves an additional benefit. The addition of oil slows the evaporation rate of the mineral spirits. By slowing the evaporation rate, you considerably reduce the amount of harmful vapor in the air. In fact, there are certain mineral spirits, like Gamsol, which are designed to evaporate 4 times slower than regular turpentine.

To clean my brushes, I simple dip them in the medium (without touching the bottom of the jar), and then squeeze out the excess paint with a rag. Anything that doesn't come off from that, is then washed away with plain soap and water.

Here's another way you can reduce the amount of vapor in your studio... Choose the right medium jar.

A large, wide mouthed jar provides a greater surface area by which the turpentine/oms can contact the air. Think of it like leaving the door wide open on a cold day... with zombies outside. By using a smaller, narrow mouthed jar, you greatly reduce the surface area of exposed solvent. Cutting your jar's mouth size in half will literally cut the vapors in half! In the same respect, if you plan on taking a break from your easel for even 5 minutes, cover your medium jar!

The absolute worst thing you could be using to hold turpentine while you work!!!

For me, just by reducing the amount of turpentine vapors in these 2 simple ways, I found that I can work comfortably without any noticeable adverse affects. Large double-doors bring in fresh air when I need it, and that's it.

(Edit: There is now a lot of useful info in the comments section. I guess an additional post is in order!)